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A/C issue on 00 GPGT

F

FordMan77

Active member
Decided to tackle the A/C issue in my GT. Here's what I know: The compressor kicks in and stays in when A/C is on. With ambient temps around 88* and the engine at idle the low side shows ~30psi and the high side see around 110. Bring the RPM's up to around 1500 and keep it there and they slowly rise. Low side gets to around 60 and slowly comes down and high side gets to 190 and no higher. Let it back to idle and can hear the compressor click a few times (almost like a cycle click but it never disengages the clutch) and the pressure returns to the 30/110 area.

The pressure cycle will repeat itself if I leave it idle long enough. I never see the high side go higher than 190.

I have dye in it and do not see any leaks. I evacuated the entire system tonight and pulled a vac down to 30 Hg and let it sit for 15 min. It showed it was holding a vacuum so I refilled the system. After the refill I get the same results. Also, the vent temps are no higher than ambient temps. I do not have dual zone A/C, all manual and the door is working as when I switch it to heat it changes and I get even hotter air (if that's possible).

Both fans come on when I have the A/C on as well.

What I did notice is that the smaller line that goes into the Evap coil is cool, but the larger line on the low side is not. I thought that that low side line should be cold and the high side should be warm/hot as it comes out of the evap? Oh, and once the system is off the low side stabilizes at around 90 and the high side at around 100.

My thought is that the compressor is bad but willing to entertain other ideas before I tear it out and replace it.
 


The low side should definitely be cool to the touch when the system is operating properly. I doubt there's a restriction in the system since the pressures aren't way out of whack, just not getting quite to where you'd want them to be. I'd expect abnormally low pressure on the low side if say the orifice tube was clogged. I would second the compressor, it could just be worn out if it's the original and has seen a lot of use.

I'm unsure of the design that GM uses on these compressors, but I know on older Honda's when the compressor gets worn it can trigger a thermal switch on the compressor and "disengage" it until it cools. I've also replaced many compressors due to age (typically above 120-150k miles on the original) that display similar conditions to what you described.
 
Had the same problem with my ac compressor just clicking I put to much Freon in evacted some and compressor started working
 
The low side tube is def. not getting any condensation/cold feeling to it. I've been researching it and it seems the orifice tube doesn't usually get clogged up on these unless the compressor blows itself up so I guess that may be out. Not sure about the design of the internals and if it disengages if it gets too hot.

I just rolled 373K today and I'm pretty sure it's the original A/C compressor on it, as when I replaced the motor at around 150K I let the compressor/lines hang while I dropped in the used motor so I didn't have to refill the system and it worked after the install. Just been the last 2 years that it began to act up.
 
Well, I yanked the system apart tonight. The accumulator looks clean, but the orifice tube looks to be f'd. I've never seen one like this.




Pardon the blurry pic, but there looks to be some type of plastic junk melted all around the outside, kinda granular. I can't peel it off and can barely blow air through it. I pulled the accumulator and don't see anything in there other than the dye I put in the system.

I have a new orifice tube and accumulator waiting to go in. My question now is, do I bother replacing the compressor too or do I just replace the accumulator, tube and flush out the lines as best as I can then button it back up, draw a vac and refill and see what I get??? I REALLY don't want to do all this just to have the compressor be shot as well. Not a fan of getting to the orifice tube if the existing compressor is going to clog up the new tube again. I think the bean counter that came up with this location should be forced to replace them for the rest of their lives... for free :th_skull:
 
Well, to answer my own question(s), here's what I did. Replaced the orifice tube, accumulator and all assoc. O-rings that I disturbed, added back the PAG oil that was lost, vac'd it for 30 min and it drew a solid 30 Hg. Let it sit for another 30 or so min. and still it held. Did not replace the compressor. Threw a can in and fired it up. Compressor kicked in and I added the correct amount of R134a. At 2K rpm vent temp is ~44*. At idle the temp is ~46*. No strange noises, no huge temp fluxes and my pressures on both sides are within specs finally.

So far it appears that the old compressor is working just fine. Time will tell if the system holds since I never did find a leak anywhere. Thank you to the 2 posters that contributed. Here's hoping it will keep on cooling for a while.
 


I bet you had moisture in the system, hence replacing the drier fixed your issue.

and yes the orfice tube is a real treat to replace on these cars! Could have been worse, you could have had to replace all the brake and fuel lines that run in that area and then 2 weeks later blow the suction line behind the brake booster and have to yank everything apart again and then 3 weeks later have your compressor take a dump. Oh wait, I lived that story and it was hell!
 
Yea, wasn't that bad for sure, lol.. Luckily for me the lines behind that area look ok. The only lines I've had to replace were both rear brake lines when I blew them out during a panic stop a while back. If my compressor decides to crap luckily I have a spare one here from when I replaced the motor.

So far the A/C has been holding out. Time will tell I guess. I really should straighten out/clean out the fins on the condenser though. The whole bottom section is pretty much flat and closed off from years of road junk. Once I get my friends car working and out of the garage I plan on trying to clean it up as best I can.
 
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